Test your diagnostic skills in our regular dermatology quiz. What is the cause of this tender lesion on a woman’s forearm?
A 55-year-old woman presents with a tender, erythematous nodule on her right forearm (Figure 1). There is no discharge from the lesion. It initially appeared five days earlier as an erythematous macule and has since developed into a nodule that is tender to palpation. She denies any trauma or insect bites to the affected area.